1. Field of the Invention
The invention is generally related to a less toxic or non-toxic substitute for mercury which has utility in a wide variety of applications, and particularly in electrical switch and sensor applications. More specifically, the invention is directed to a gallium based metallic material which will behave like mercury metal at both high and low temperatures.
2. Description of the Prior Art
Mercury is used extensively in switches and sensors. In a common switch application, liquid mercury is positioned inside a fluid tight housing into which a pair of spaced electrodes extend. Depending on the physical orientation of the housing, the liquid mercury can provide a conductive pathway between the electrodes or be positioned such that there is an open circuit between the electrodes. An important physical attribute of mercury is that it remains fluid throughout a wide temperature range. This attribute allows mercury to be used in many different environments and in environments with constantly changing temperature parameters. Another important physical attribute of mercury is that it has significant surface tension and does not wet glass, metal or polymer surfaces. However, mercury is toxic to humans and animals. As such, finding less toxic or non-toxic alternatives to mercury that have comparable performance characteristics would be beneficial.
Gallium alloys have been proposed as a substitute liquid metal for mercury in electrical switch applications in both U.S. Pat. No. 3,462,573 to Rabinowitz and in Japanese Patent Application Sho 57-233016 to Inage et al. U.S. Pat. No. 3,462,573 to Rabinowitz suggests the use of gallium alone, as well as binary, ternary and quaternary alloys of gallium, in electrical switches. Rabinowitz indicates that adding elements to gallium can be used as a means to lower the freezing point or solidification temperature of the combination below the freezing point of gallium alone (29.7.degree. C.). The metals selected must be soluble in gallium and include indium, tin, copper, silver, gold, palladium, iron, germanium, zinc, calcium, nickel, cadmium, and platinum. Particularly preferred gallium alloys identified in Rabinowitz include gallium-indium-tin alloys. Japanese Patent Application Sho 57-233016 to lnage et al. discloses that using 1-3.5% silver in combination with gallium-indium-tin alloys can lower the solidification temperature of the alloy close to 0.degree. C.
It would be advantageous to provide a non-mercury metallic material which has a solidification temperature below 0.degree. C., and which does not include heavy metals which pose potential health hazards such as mercury, cadmium, lead, chromium, or tin.